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For commercial-vehicle Original Equipment Manufacturers (OEMs), predictive maintenance has drawn attention for the benefits of money saving and increased road safety. Data-driven models have been widely explored and implemented as predictive maintenance solutions. However, the working scenarios for different commercial-vehicles vary a lot, which makes it difficult to build a universal model suitable for all the cases. In this paper, we propose a Recurrent Neural Adaptive Processes (RNAPs) network to adapt to different scenarios by modeling the uncertain at the same time. The ensemble network combines the traits of neural processes, recurrent neural network and meta learning together. Neural processes consider the context information to calculate the uncertainty and improve the prediction results. Meta-learning works well when dealing with few-shot multi-tasks learning, and recurrent networks are utilized as the encoder of the proposed model to process time-series data.

A fuel reforming technology using a low temperature oxidation was developed to improve a NOx reduction performance of HC-SCR (Hydrocarbons Selective Catalytic Reduction) system, which does not require urea. The low-temperature oxidization of a diesel fuel in gas phase produces NOx reduction agents with high NOx reduction ability such as aldehydes and ketones. A pre-evaporation-premixing-type reformer was adopted in order to generate a uniform temperature field and a uniform fuel/air premixed gas, and to promote the low temperature oxidation efficiently. As a fundamental study, elementary reaction analysis for n-hexadecane/air premixtures was carried out to investigate the suitable reformer temperature and fuel/air equivalence ratio for generation of oxygenated hydrocarbons. It was found that the reforming efficiency was highest at the reforming temperature around 623 to 673K, and aldehydes and ketones were produced.

Understanding and prediction of flash-boiling spray behavior in gasoline direct-injection (GDI) engines remains a challenge. In this study, computational fluid dynamics (CFD) simulations using the homogeneous relaxation model (HRM) for not only internal nozzle flow but also external spray were evaluated using CONVERGE software and compared to experimental data. High-speed extinction imaging experiments were carried out in a real-size axial-hole transparent nozzle installed at the tip of machined GDI injector fueled with n-pentane under various ambient pressure conditions (Pa/Ps = 0.07 - 1.39). The width of the spray during injection was assessed by means of projected liquid volume, but the structure and timing for boil-off of liquid within the sac of the injector were also assessed after the end of injection, including cases with different designed sac volumes.

An accurate prediction of internal nozzle flow in fuel injector offers the potential to improve predictions of spray computational fluid dynamics (CFD) in an engine, providing a coupled internal-external calculation or by defining better rate of injection (ROI) profile and spray angle information for Lagrangian parcel computations. Previous research has addressed experiments and computations in transparent nozzles, but less is known about realistic multi-hole diesel injectors compared to single axial-hole fuel injectors. In this study, the transient injector opening and closing is characterized using a transparent multi-hole diesel injector, and compared to that of a single axial hole nozzle (ECN Spray D shape). A real-size five-hole acrylic transparent nozzle was mounted in a high-pressure, constant-flow chamber. Internal nozzle phenomena such as cavitation and gas exchange were visualized by high-speed long-distance microscopy.

An on board burner that enables DPF regeneration even when an engine is at standstill has been researched. By employing pre evaporative combustion with a wick burner, miniaturization of the burner system was successfully accomplished as well as stable ignition and combustion. Total heat necessary for DPF regeneration was reduced in comparison to the active DPF regeneration by means of engine control and an oxidation catalyst. Uneven temperature distribution in DPF and excessive temperature rise, which had been recognized as issues in the regeneration of a DPF while engine is at standstill, were solved by increase of combustion air amount and multi-step control of regeneration temperature and reliable regeneration was accomplished.

The change in the smoke emissions from a diesel engine with the shapes of the combustion chamber and the in-cylinder density was investigated with focuses on the mixing and the soot formation in a spray flame. First, the mixing of the fuel and air between the nozzle exit and the set-off length was used as an indicator for the formation of soot. Although this indicator can explain the influence of the density, it cannot explain the changes in the smoke emissions with a change in the shape of the combustion chamber. Next, by focusing on the soot distribution in a quasi-steady-state spray flame, the soot formed in the high-density condition of an optically accessible engine was investigated by applying two-color method. These results showed that the positional relationship between the maximum soot amount position and the flame impinging position can be a major influence on the smoke emissions.

As engines become lighter and achieve higher output to meet carbon dioxide emissions targets, it becomes more challenging to design a crankshaft that is both lighter and capable of handling higher loads. Therefore, it is necessary to understand the characteristics of forces imposed on the crankshaft, and the mechanisms by which stresses are created in the crankshaft. This paper describes the characteristics of bending stresses measured on the rearmost crank pin fillet of a crankshaft. Two basic crankshaft resonant modes are described. Forward crankshaft whirl then has the effect of increasing the system natural frequencies by the stiffening effect, while reverse whirl reduces the system natural frequencies by the softening effect. The effect of whirl grows with increasing engine speed. This results in what appears to be four crankshaft natural frequencies rather than two. The four resonances appear at all non-zero engine speeds.

In recent years, start-stop systems have been implemented by many OEMs for improvement of fuel economy. When the engine stops, the occupant comfort typically deteriorates. Hence, the climate and fuel economy engineers are struggling to combine the passenger comfort and fuel economy. Especially in a vehicle cabin where the thermal environment becomes unsteady and highly non-uniform due to a start-stop. It is difficult to adapt any comfort evaluation index that have already been well established for a stationary/uniform space in building type environment in comparison to a vehicle cabin interior. The existing standard of ISO-14505-2 does not consider this for vehicle cabin interior condition. Hence, the authors have developed the occupant’s comfort prediction method under highly non-uniform condition and unsteady conditions and have established a new methodology [1].

As a result of WNTE regulations and the introduction of close-coupled aftertreatment systems, exhaust purification at high temperatures in commercial vehicles has become increasingly important in recent years. In this report, we improve the prediction accuracy for NOx conversion at high temperatures in the kinetic model of conventional Cu-selective catalytic reduction (Cu-SCR). Reaction rate analysis indicated that the rate of NH3 oxidation was extremely low compared to the rate of standard SCR. We found that NOx concentration-dependent NH3 oxidations (termed NOx-assisted NH3 oxidations) were key to the rate of NH3 oxidation. The output of the improved Cu-SCR kinetic model was in agreed with experimental results obtained from the synthetic gas bench and engine dynamometer bench. We analyzed the contribution of each reaction to NH3 consumption during Cu-SCR. Under NH3 + NO + O2, standard SCR was dominant at low temperature.

The correlation between newly approved EN 15751 and the internal diesel injector deposits (IDID) due to fuel oxidative deterioration has not been made clear. In the present research, the Rancimat method was slightly modified to research the relationship between fuel oxidative deterioration and the deterioration products generated from the fuel. After heating fuel at 120 to 150°C for a set period, insoluble deterioration products (IDID-like substances) were generated and their weights were measured. At the same time, the shifts of the conductivity in trap water were analyzed from a new perspective, and its relationship with the deterioration products was investigated. At 120°C and 130°C, conductivity rising rates after the inflection point (this set of data represents the rate of organic acid generation in the fuel, and we named “Oxidation rate”) exhibited a strong correlation with the quantity of deterioration products.

To improve the thermal efficiency of an engine, it is particularly important to reduce the cooling loss from the combustion gas to the combustion chamber wall, which constitutes a major proportion of the total loss [1]. Previous studies addressing cooling loss reduction attempted to use ceramic in place of the conventional aluminum or iron alloys, but this led to a reduction in the volumetric efficiency and increased smoke emissions. This was caused by the ceramics having both a low thermal conductivity and high heat capacity, relative to aluminum and iron. These characteristics cause the piston wall temperature, which rises during combustion, to remain high during the intake stroke, thus increasing the intake temperature and reducing the volumetric efficiency. This increases the smoke emissions [2].

In Thailand, most heavy-duty trucks were equipped with diesel engine, while a small portion was equipped with compressed natural gas (CNG) engine. However, in the past few years the number of CNG fuel trucks in Thailand has increased significantly due to the cheaper cost of CNG. In general, the emphasis of heavy-duty diesel engine oil performance is on piston cleanliness and soot handling properties, while thermal and anti-oxidation properties are most critical for CNG engine oil performance. For truck fleet owners who operate both types of trucks, using the inappropriate oil that is not fit-for-purpose can adversely affect engine performance and reduce engine service lifespan under prolonged usage. A novel CNG/diesel engine oil was developed to meet both JASO DH-2 heavy-duty diesel engine oil performance and CNG engine oil performance. The candidate formulation was proved adequately fit for practical use regarding to thermal and anti-oxidation properties.

A diesel engine is advantageous in its high thermal efficiency, however it still wastes about 50% of total input energy to exhaust and cooling losses. A feasibility study of thermoacoustic refrigerator was carried out as one of the means to recuperate waste heat. The thermoacoustic refrigerator prototyped for this study showed a capability to achieve cooling temperature lower than -20 degree C, which indicated that the system has a potential to be used in refrigerator trucks not only for cargo compartment cooling but also for cabin cooling.

In recent years, although experiment technologies on real engines and simulation technologies has been improved rapidly, the tribology contributing factors have not been quantitatively well evaluated to reveal critical lubrication failure mechanisms. In this study the oil film thickness of the main bearings in multicylinder diesel engines was measured, and the data was analyzed using response surface methodology, which is a statistical analysis methods used to quantitatively derive the factors affecting oil film thickness and the extent of their contribution. We found that the factor with the strongest effect on minimum oil film thickness is oil pressure. Lastly, as a verification test, bearing wear on the main bearings was compared under various oil pressure conditions. Clear differences in bearing wear were identified.

In order to improve the brake thermal efficiency of the engine, such as cooling and friction losses from the theoretical thermal efficiency, it is necessary to minimize various losses. However, it is also essential to consider improvements in theoretical thermal efficiency along with the reduction of the various losses. In an effort to improve the brake thermal efficiency of heavy-duty diesel engines used in commercial vehicles, this research focused on two important factors leading to the engine's theoretical thermal efficiency: the compression ratio and the specific heat ratio. Based on the results of theoretical thermodynamic cycle analyses for the effects of the above two factors, it was predicted that raising the compression ratio from a base engine specification of 17 to 26, and increasing the specific heat ratio would lead to a significant increase in theoretical thermal efficiency.

Wear resistance is the important characteristics of cast iron materials for automobile components. Because the phenomenon of wear is a highly complicated mechanism involving many factors such as surface conditions, chemical reactions with lubricants, metals, and physics, it has not been fully explained. Therefore, it will be necessary to confirm and explain the wear mechanism to develop effective improvements. The purpose of this study was to investigate the structural change behavior and effects of alloying elements when the material top surface becomes worn, in order to improve the wear resistance of cylinder liners and other cast iron materials. For this purpose, several types of prototype materials were produced, and the relationship between components and wear resistance was investigated by using a laser microscope for quantitative observation of the degree of pearlite microstructure fineness.

Reducing friction between the piston ring and cylinder is an effective way of meeting the demand for lower fuel consumption in vehicle engines. To that effect, the authors have proposed a new and efficient friction reduction treatment for the cylinder. At first glance, this treatment seems similar to typical microtexture treatments, but it is built on a different approach. Through a rig tester, it was confirmed that optimizing the shape of the dimples and the treatment area for the cylinder improves FMEP between the piston ring and the cylinder liner by 17%. This report presents an analysis of the test results to explain the mechanism by which this effect is achieved. Fuel consumption was measured in an actual engine, and a maximum fuel consumption improvement of 3.2% was confirmed after conversion to the Japanese heavy duty vehicle fuel economy standards (Category T2). Lubricating oil consumption, blow-by and durability were also examined.

1 To meet the Japan Post New-Long-Term (Japan 2009) emissions regulation introduced in 2009, The Hydrocarbon Selective Catalytic Reduction (HC-SCR) system for the NOx emission with a diesel fuel was chosen among various deNOx after-treatment systems (the Urea-SCR, the NOx storage-Reduction Catalyst and so on). The HC-SCR was adopted, in addition to combustion modification of diesel engine (mainly cooled EGR) as the New DPR system. The New DPR system for medium and light duty vehicles was developed as a world's first technology by Hino Motors. Advantages of the New DPR are compact to easy-to-install catalyst converter and no urea solution (DEF) injection (regardless urea infrastructure) as compared the Urea-SCR system.

In heavy duty (HD) trucks cruising on expressway, about 60% of input fuel energy is wasted as losses. So it is important to recover them to improve fuel economy of them. As a waste heat recovery system, a Rankine cycle generating system was selected. And this paper mainly reports it. In this study, engine coolant was determined as main heat source, which collected energies of an engine cooling, an EGR gas and an exhaust gas, for collecting stable energy as much as possible. And the exergy of heat source was raised by increase coolant temperature to 105 deg C. As for improving the system efficiency, saturation temperature difference was expanded by improving performance of heat exchanger and by using high pressure turbine. And a recuperator which exchanges heat in working fluid between expander outlet and evaporator inlet was installed to recover the heat of working fluid at turbine generator. Then a working fluid pump was improved to reduce power consumption of the system.

Diesel engine has a good fuel economy and high durability and used widely for power source such as heavy duty in the world. On the other hand, it is required to reduce NOx (Nitrogen Oxides) and PM (Particulate Matter) emissions further from diesel exhaust gases to preserve atmosphere. The urea-SCR (Selective Catalytic Reduction) system is the most promising measures to reduce NOx emissions. DPF (Diesel Particulate Filter) system is commercialized for PM reduction. However, in case that a vehicle has a slow speed as an urban area driving, a diesel exhaust temperature is too low to activate SCR catalyst for NOx reduction in diesel emissions. Moreover, the diesel exhaust temperature becomes lower as a future engine has less fuel consumption. The purpose of this study is reduction of NOx emission from a heavy-duty diesel engine using the Urea SCR system at the low temperature.